Basically I am set out to build a power analyzer,
which will include :-
-1 phase supply monitoring-
-Surge detection capabilities of the order of 10 microseconds
-Data logging at configurable intervals
-Current harmonics distortion calculation
-Measurement of parameters -True rms I & V, KVA, KVAR , cos(phi)

I need to find out how to measure the power factor
from the AC mains supply using a DSP microntroller and MATLAB for
demonstration purpose. So far I have reached a stage where I can
acquire data using a conditioning circuit which includes a CT and a PT,
followed by Instru. Amp. I tried looking for algorithms for measurement
of these factors over the internet but didn't get any threads on the PF
front.
I would be really grateful if somebody could help
me out with this.
Thanking you in anticipation.

Chetan.

On 1 Nov 2006 21:27:57 -0800, "chetanthegreat"
wrote:

Basically I am set out to build a power analyzer,
which will include :-
-1 phase supply monitoring-
-Surge detection capabilities of the order of 10 microseconds
-Data logging at configurable intervals
-Current harmonics distortion calculation
-Measurement of parameters -True rms I & V, KVA, KVAR , cos(phi)

I need to find out how to measure the power factor
from the AC mains supply using a DSP microntroller and MATLAB for
demonstration purpose. So far I have reached a stage where I can
acquire data using a conditioning circuit which includes a CT and a PT,
followed by Instru. Amp. I tried looking for algorithms for measurement
of these factors over the internet but didn't get any threads on the PF
front.
I would be really grateful if somebody could help
me out with this.
Thanking you in anticipation.

Chetan.
Rather simple to measure phase angle

You take the zero crossing of the incoming line voltage and compare it
to the zero crossing of the current shunt at the load side.

Ordinary op amps have gain of ~200,000, so with just a few glue
components you can get the low to high transition of both the voltage
and current simply by overdriving the op amps. (protecting them from
reverse and over voltage with some clamping diodes - and signal
massaging) You get a square wave.

The two transitions are offset in time depending on phase angle - that
can be translated and integrated to an analog voltage signal to
average it and sample when the processor has the time or the processor
can take time off to look at the phase angle periodically, or measured
directly in real time with a fast or dedicated processor.

Phase angle changes rapidly with some loads - an induction motor
driving a sticky V belt or with a inconsistent load - like a wash
machine agitator. Other loads are less variable.

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